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A221455 Number of 0..4 arrays of length n with each element unequal to at least one neighbor, with new values introduced in 0..4 order. 1
0, 1, 2, 7, 25, 101, 436, 1971, 9159, 43262, 206285, 988963, 4755888, 22910979, 110480787, 533057462, 2572761417, 12419474751, 59958562568, 289483787719, 1397691920591, 6748491159958, 32584154032229, 157329000870907 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
Column 4 of A221459.
LINKS
FORMULA
Empirical: a(n) = 7*a(n-1) - 7*a(n-2) - 20*a(n-3) + 10*a(n-4) + 24*a(n-5) + 8*a(n-6).
Empirical g.f.: x^2*(1 - 5*x + 10*x^3 + 5*x^4) / ((1 - x - x^2)*(1 - 2*x - 2*x^2)*(1 - 4*x - 4*x^2)). - Colin Barker, Aug 05 2018
EXAMPLE
Some solutions for n=6:
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..1....1....1....1....1....1....1....1....1....1....1....1....1....1....1....1
..1....2....0....0....2....2....2....2....2....2....2....0....2....0....1....2
..0....1....2....2....1....3....2....1....0....3....0....0....3....2....2....0
..1....1....2....3....3....4....3....3....1....0....3....2....2....2....3....3
..0....2....3....1....2....0....4....0....0....2....2....1....1....0....2....1
CROSSREFS
Cf. A221459.
Sequence in context: A150498 A150499 A150500 * A150501 A150502 A150503
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 17 2013
STATUS
approved

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Last modified July 16 10:51 EDT 2024. Contains 374345 sequences. (Running on oeis4.)